KR100542513B1 - Optical disk recording method - Google Patents

Abstract

The present invention relates to an optical disc, an optical disc apparatus, and an optical disc recording method. For example, when the present invention is applied to a compact disc, the jitter at the time of reproduction is reduced and the recorded data can be surely reproduced. The change pattern of the modulation signal S2 is detected, the timing of the modulation signal S1 is corrected according to this change pattern, and the laser beam L is irradiated.

Optical disc, optical disc device, optical disc recording method

Description

Optical disc recording method {OPTICAL DISK RECORDING METHOD}

1 is a block diagram showing an optical disk device according to a first embodiment of the present invention.

2 is a signal waveform diagram used to explain the operation of the edge position correction circuit included in the optical disk device of FIG.

3 is a block diagram showing a rising edge correction circuit included in the optical disk device of FIG.

4 is a process chart showing a process of generating a correction value table included in the optical disk device of FIG.

FIG. 5 is a flowchart showing a processing procedure of a computer in the process of FIG. 4. FIG.

6 is a block diagram showing an optical disk device according to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a signal generation circuit included in the optical disk device of FIG.

FIG. 8 is a plan view showing a compact disk produced by the optical disk device of FIG. 6; FIG.

9 is a signal waveform diagram showing a reproduction signal of a portion of a compact disc using 100% light quantity.

Fig. 10 is a signal waveform diagram showing a reproduction signal of a portion of a compact disc using 85% light quantity.

Fig. 11 is a signal waveform diagram showing a change in slice level caused by a difference in light amount.

12 is a signal waveform diagram showing a reproduction signal obtained from the compact disc of FIG. 8 in comparison with FIG.

<Explanation of symbols for the main parts of the drawings>

1, 50: optical disk device

2: disc disk

13: modulation circuit

14, 57A, 57B: edge position correction circuit

17A: rising edge correction circuit

17B: falling edge correction circuit

20: correction value table

22: delay circuit

23: selector

51: signal generation circuit

The present invention relates to an optical disc, an optical disc apparatus, and an optical disc recording method. The present invention is also applied to a compact disc, for example. By correcting the timing of the modulation signal in accordance with the change pattern of the modulation signal, jitter at the time of reproduction is reduced and recorded data can be reliably reproduced.

In conventional compact discs, data to be recorded is subjected to data processing and then EFM (Eight-to-Fourteen Modulation) modulation. For a given basic period T, a pit sequence is formed with a period in the range of 3T to 11T. Accordingly, audio data and the like are recorded, for example.

Correspondingly, the compact disc player irradiates a laser beam on the compact disc and receives the returned light. The compact disc player obtains a reproduction signal whose signal level changes in accordance with the amount of light of the returned light, converts the reproduction signal into a binary value using a predetermined slice level, and generates a binary signal. In addition, the compact disc player drives the PLL circuit in response to this binary signal to generate a reproduction clock and sequentially latches the binary signals using the reproduction clock. Accordingly, the compact disc player generates playback data corresponding to the pit rows formed on the compact discs with periods ranging from 3T to 11T.

The compact disc player performs data processing corresponding to the data processing performed at the time of recording on the data thus reproduced. In this way, the compact disc player plays back audio data and the like recorded on the compact disc.

By the way, in the conventional compact disc player, jitter is contained in a reproduction signal. This jitter can be considered to be caused by various causes such as noise of a laser beam used for reading, thermal noise of an electrical system, disk noise, and the like. Jitter lowers the phase margin of the reproduction signal. In extreme cases, jitter makes it difficult to reproduce accurate data.

However, this jitter is inherently due to inter-symbol interference caused by front and back pits (Shigeo Kubota, "Aplanatic condition required to reproduce jitter-free signals in an optical digital disk system", App Optics 1987, Vol. 26, No. 18, pp. 3961-3970). Jitter changes with lands and pits located before and after the laser beam irradiation position.

In view of the points described above, the present invention has been made. It is an object of the present invention to propose an optical disc, an optical disc apparatus, and an optical disc recording method capable of reducing jitter generated during reproduction and reliably reproducing recorded data.

In order to solve the above problems, in the optical disk apparatus and the optical disk recording method according to the present invention, the timing of the modulated signal is corrected according to the change pattern of the modulated signal.

Further, in the optical disc, the position of the edge is changed from its basic position according to the pit length and the land length located before and after the edge.

Further, in the optical disk apparatus and the optical disk recording method, the timing of raising the laser beam to the amount of light for recording is corrected in conjunction with switching the amount of light of the recording operation.

In addition, in the optical disk, a high reflectance region and a low reflectance region are formed according to the difference in the pit widths. In order to correct the change in the feedback light caused by the difference in the pit widths, the pits to which the same data is allocated are formed to have different pit lengths.

By correcting the timing of the modulated signal, it is possible to correct a change in the signal level during reproduction. If this timing correction is performed based on the change pattern of the modulation signal, the reproduction signal can be corrected so as to correct the intersymbol interference that changes according to this change pattern. As a result, jitter in the reproduction signal can be reduced.

In the optical disc, correspondingly, the position of the edge is changed from its basic position according to the pit length and land length located before and after the edge. Accordingly, the pit shape is changed to correspond to the change pattern of the modulated signal. As a result, jitter caused by inter-signal interference can be avoided.

In addition, if the timing of raising the laser beam to the amount of light for recording is corrected in conjunction with the switching of the amount of light of the recording operation, it is possible to correct an asymmetry changed by the amount of light switching.

Correspondingly, in the optical disk, high reflectance regions and low reflectance regions are formed in accordance with the difference in the pit widths. Accordingly, text and the like can be recorded on the information recording surface for visual observation. In this case, if the pits to which the same data is assigned are formed to have different pit lengths in order to correct the change in the feedback light caused by the difference in the pit width, different asymmetry can be corrected in the high reflectivity region and the low reflectance region.

DESCRIPTION OF EMBODIMENTS An optical disc, an optical disc apparatus, and an optical disc recording method according to embodiments of the present invention will be described below with appropriate reference to the accompanying drawings.

<First Embodiment>

1 is a block diagram showing an optical disk device according to a first embodiment of the present invention. This optical disc apparatus 1 records audio data D1 output from the digital audio tape recorder 3 by exposing the disc master 2 to light. In the manufacturing process of an optical disk, after developing this disk original disk 2, an electroforming process is performed. As a result, a mother disk is created. From this mother disk, a stamper is created. Further, in the optical disk manufacturing process, a disk-shaped substrate is produced from the stamper thus produced. By forming a reflecting film and a protective film on this disk-shaped board | substrate, a compact disk is produced | generated.

In other words, in this optical disk apparatus 1, the spindle motor 4 drives and rotates the disk disk 2. From the FG signal generator supported at the bottom thereof, an FG signal FG whose signal level rises at every predetermined rotation angle is output. According to the exposure position of the disc master 2, the spindle servo circuit 5 drives the spindle motor 4 so that the frequency of this FG signal is equal to a predetermined frequency. As a result, the disc disc 2 is driven to rotate under the condition of a constant linear velocity.

The recording laser 7 is constituted by a gas laser or the like and emits a laser beam L for disc disc exposure. The light modulator 8 is composed of an electroacousto-optic element and emits on and off the laser beam L by using the modulation signal S1. The mirror 10 bends the optical path of the laser beam L and radiates toward the disc disk 2. The objective lens 11 condenses the light reflected by the mirror 10 on the disk master 2. The mirror 10 and the objective lens 11 are sequentially moved in the radial direction of the disk master 2 in synchronism with the rotation of the disk master 2 by a sled mechanism (not shown). As a result, the exposure position of the laser beam L is sequentially displaced in the circumferential direction of the disc master 2.

In the optical disk apparatus 1, in the state where the optical disk 2 is driven and rotated, tracks are formed spirally by the movement of the mirror 10 and the objective lens 11, and the tracks are modulated by the modulation signal S1. Correspondingly, pits are formed sequentially.

Audio data D1 is input from the digital audio tape recorder 3 to the modulation circuit 13. In addition, subcode data corresponding to the audio data D1 is input to the modulation circuit 13. The modulation circuit 13 performs data processing on the audio data D1 and the subcode data by using a data processing method defined for the compact disc. That is, the modulation circuit 13 adds an error correction code to the audio data D1 and the subcode data, and then interleaves it, and then performs EFM modulation to output the EFM signal S2.

The edge position correction circuit 14 detects a change pattern of the EFM signal S2 and corrects the timing of the EFM signal S2 so as to effectively avoid inter-signal interference during reproduction according to this change pattern.

Specifically, in the edge position correction circuit 14, the level converting circuit 15 corrects the signal level of the EFM signal S2 having an output amplitude of 1 [V] to a TTL level having an output amplitude of 5 [V] and outputs it. . The PLL circuit 16 generates and outputs the clock CK (Fig. 2 (b)) from the EFM signal S2 (Fig. 2 (a)). In the EFM signal S2, the signal level changes in a period of 3T to 11T with respect to the basic period T. Therefore, the PLL circuit 16 generates a clock CK whose signal level changes in accordance with the basic period T synchronized with this EFM signal S2.

As shown in Fig. 3, the rising edge correction circuit 17A includes thirteen latch circuits 19A to 19M connected in series and operated by a clock CK. The output signal S3 of the level converting circuit 15 is input to the series circuits of the latch circuits 19A to 19M. The rising edge correction circuit 17A samples the output signal S3 of the level conversion circuit 15 by the timing of the clock CK, and detects the change pattern of the EFM signal S2 based on the sampling result of 13 consecutive points. That is, for example, when a latch output of “0001111000001” is obtained, it can be determined as a change pattern including pits of length 4T consecutive after a space of length 5T. Similarly, when a latch output of “0011111000001” is obtained, for example, it can be determined as a change pattern including pits of length 5T consecutive after a space of length 5T.

The correction value table 20 is formed of a read only memory which stores a plurality of correction data. Using the latch outputs of the latch circuits 19A to 19M as addresses, the correction value table 20 outputs correction value data DF corresponding to the change pattern of the EFM signal S2. The monostable multivibrator (MM) 21 receives as a input the latch output of the latch circuit 19G located at the center of the thirteen latch circuits 19A to 19M connected in series. Using the rising timing of the latch output as a reference, the monostable vibrator 21 outputs a rising pulse signal in which the signal level rises for a predetermined time interval (interval sufficiently shorter than the period 3T).

Delay circuit 22 has twelve stage tap outputs. The delay time difference between each tap is set equal to the resolution of timing correction of the modulated signal in the edge position correction circuit 14. The delay circuit 22 sequentially delays the rising pulse signal output from the monostable multivibrator 21 and outputs the delayed signal from each tap. The selector 23 selects and outputs the tap output of the delay circuit 22 according to the correction value data DF. As a result, the rising pulse signal SS (Fig. 2 (d)) whose delay time changes in accordance with the correction value data DF is selected and output.

Accordingly, the rising edge correction circuit 17A generates the rising edge signal SS whose signal level rises in response to the edge rising of the signal level of the EFM signal S2. Delay times Δr (3, 3), Δr (4, 3), Δr (3, 4), Δr (5, 3),... Is changed according to the corresponding rising edges of the EFM signal S2, that is, the change pattern of the EFM signal S2 detected by the sampling before and after a total of 13 times.

In Fig. 3, the change pattern of the modulation signal S2 is represented by the pit length p and the pit interval b in units of one period of the clock (i.e., channel clock) CK. The delay time from the rising edge is represented by Δr (p, b). Therefore, in Fig. 2 (d), the second delay time Δr (4, 3) is a delay time when there is a blank of three clocks ahead of the pit of four clocks in length. In the correction value table 20, correction value data corresponding to all combinations of p and b are stored in advance.

In general, the compact disc is exposed to the laser beam L in accordance with the EFM signal S2 and pits are formed thereon. For the range of 12T on the basis of the basic period T, the rising edge correction circuit 17A detects a pattern of pits formed on the compact disc, and generates the rising edge signal SS in accordance with this pattern.

The falling edge correction circuit 17B has the same configuration as the rising edge correction circuit 17A except that the monostable multivibrator 21 operates based on the falling edge of the latch output and that the contents of the correction value table 20 are different. Have

Accordingly, the falling edge correction circuit 17B generates the falling edge signal SR (Fig. 2 (c)) in which the signal level rises in response to the falling of the signal level of the EFM signal S2. Delay times Δf (3, 3), Δf (4, 4), Δf (3, 3), Δf (5, 4),... Is changed according to the corresponding falling edges of the EFM signal S2, that is, the change pattern of the EFM signal S2 detected by a total of 13 samplings. In FIG. 3, the delay time from each falling edge is expressed as Δf (p, b) using the pit length p and the pit spacing b as well as the delay time for the rising edge.

For a range of 12T based on the basic period T, the falling edge correction circuit 17B detects a pattern of pits formed on the compact disc and, according to this pattern, an EFM signal which functions as the timing of the end of exposure of the laser beam. The timing of the falling edge of S2 is corrected to generate the falling edge signal SR.

Flip-flop (F / F) 25 (FIG. 1) outputs a combination of rising edge signal SS and falling edge signal SR. That is, the rising edge signal SS and the falling edge signal SR are input to the set terminal S and the reset terminal R of the flip flop 25, respectively. As a result, the flip flop 25 generates a modulation signal S5 in which the signal level falls in response to the rising edge of the falling edge signal SR after the signal level rises in response to the rising edge of the signal level in the rising edge signal SS. The level inverse conversion circuit 26 corrects the signal level of this modulated signal S5 whose output amplitude is the TTL level, and outputs it at the original output amplitude of 1V.

As a result, the modulation signal S1 corrected in accordance with the pit length and the land length in which the timings of the rising edge and the falling edge are located before and after is output. Correspondingly, the timing at which the disc master 2 is exposed to the laser beam L is also corrected according to the pit length and the land length located before and after. Therefore, in the compact disc produced by this disc master 2, each edge position changes from its basic position according to the pit length and land length located before and after. As a result, the pit length is changed between the pits to which the same data is assigned. Accordingly, the optical disk apparatus 1 corrects the positions of the front edge and the rear edge of each pit so as to reduce jitter caused by inter-signal interference during reproduction.

4 is a flowchart for explaining the generation of the correction value table 20 used to correct the edge timing as such. In the optical disk apparatus 1, by appropriately setting this correction value table 20, the positions of the front edge and the rear edge of each pitch can be set to the optimum position, and the reproduction signal is in accordance with the correct timing synchronized with the clock CK. Can be changed. Specifically, even when the pit size and length of the front and back blanks are changed, the reproduction signal passes through a predetermined slice level at the correct timing synchronized with the clock CK. As a result, a reproduction signal with reduced jitter can be obtained. The correction value table 20 exists in both the rising edge correction circuit 17A and the falling edge correction circuit 17B. The setting method is the same for all of them. Therefore, the description will be limited only to the rising edge correction circuit 17A here.

In this step, a correction value table is set on the evaluation disc master by the optical disc apparatus 1 on the basis of the reproduction result of the compact disc generated from this disc master.

When generating this disk for evaluation, the evaluation value correction value table 20 is set in the optical disk apparatus 1. The correction value data DF is set in this evaluation reference correction value table 20 so that the selector 23 always selects and outputs the center tap output of the delay circuit 22. Therefore, in this step, the disc master 2 is exposed to light under the same conditions as when the optical modulator 8 is directly driven by the EFM signal S3, that is, under the same conditions as the conventional compact disc generating process.

In this step, the disk master 2 thus exposed to light is developed and then subjected to an electroforming process. As a result, a mother disk is created. From this mother disk, a stamper 40 is generated. In addition, the compact disc 41 is produced from the stamper 40 as in the conventional compact disc generating process.

The compact disc player (CD player) 42 reproduces the evaluation compact disc 41 thus generated. At this time, the compact disc player 42 switches the operation under the control of the computer 44, and outputs the reproduction signal RF to the digital oscilloscope 43 from the built-in signal processing circuit. This reproduction signal RF changes in signal level in accordance with the amount of light of the feedback light obtained from the compact disc and is output from the output of the optical pickup through a predetermined buffer circuit. Thus, this compact disc 41 is created under the same conditions as a normal compact disc. If this reproduction signal RF is observed on the digital oscilloscope 43 using the reproduction clock as a trigger, jitter can be observed.

The digital oscilloscope 43 switches the operation under the control of the computer 44, analog-to-digital converts the reproduction signal RF to a sampling frequency 20 times the channel clock frequency, and converts the resulting digital signal into the computer 44. Output to.

In addition to controlling the operation of the digital oscilloscope, the computer 44 also processes the digital signal output from the digital oscilloscope 43 and accordingly calculates the correction data RF. In addition, the computer 44 drives the ROM writer 45 and sequentially stores the correction value data DF calculated in the read-only memory, thereby forming the correction value table 20. In this step, a compact disc is finally manufactured using this correction value table 20.

5 is a flowchart showing a processing procedure in the computer 44. In this processing procedure, the computer 44 proceeds from step SP1 to step SP2 to set the jitter detection result Δr (p, b) and jitter measurement number n (p, b) to zero. Around each edge that is the jitter detection target, the computer 44 calculates the jitter detection result Δr (p, b) for each combination of the pit length p and the pit interval b, and counts the number of jitter measurements n (p, b). . Therefore, in step SP2, the computer 44 sets all jitter detection results Δr (p, b) and jitter measurement number n (p, b) to initial values.

Thereafter, the computer 44 proceeds to step SP3. The computer 44 converts the reproduction signal RF into a binary value by generating a digital binary signal by comparing the digital signal output from the digital oscilloscope 43 with a predetermined slice level. In this process, computer 44 converts the digital signal to a binary value to provide a value of 1 for the digital signal above the slice level and a value of 0 for the digital signal below the slice level.

Thereafter, the computer 44 proceeds to step SP4 to generate a reproduction clock from the binary signal formed from the digital signal. Here, the computer 44 simulates the operation of the PLL circuit by performing calculation processing based on the binary signal, thereby generating a reproduction clock.

In a subsequent step SP5, the computer 44 samples the binary signal at the timing of each falling edge of the regenerated clock so generated and decodes the EFM signal accordingly (hereinafter referred to as the decoded EFM signal into a decoded EFM signal). Call).

The computer 44 then proceeds to step SP6 to detect the time difference e measured from the time of the rising edge of the binary signal to the time of the rising edge of the reproduction clock closest to the edge. Accordingly, computer 44 measures the time of jitter at this edge. Then at step SP7, the computer 44 detects the pit length p before and after and the pit spacing b from the decoded EFM signal for the timed edge at step SP6.

Then, in step SP8, the computer 44 adds the time difference e detected in step SP6 to the jitter detection result Δr (p, b) corresponding to the pit length p and the pit interval b before and after, and the corresponding jitter measurement number n Increment (p, b) by 1 The computer 44 then proceeds to step SP9 to determine whether the time measurement has been completed for all rising edges. If a negative result is obtained here, the computer returns to step SP5.

As a result, the computer 44 repeats the processing sequence of steps SP5-SP6-SP7-SP8-SP9-SP5, accumulates the time-measured jitter detection results for every change pattern appearing in the reproduction signal RF, and adds the addition number. Count.

If the jitter time measurement is completed for all edges, a positive result is obtained at step SP9. As a result, the computer 44 proceeds to step SP10. For each change pattern that appears in the reproduction signal RF, the computer averages the time-measured jitter detection results. In other words, the jitter detected at step SP6 is affected by noise. By averaging the jitter detection results, the computer 44 improves the accuracy of the jitter measurement.

If so averaged jitter detection results, computer 44 then proceeds to step SP11. Based on the detection result, the computer generates correction value data DF for each change pattern and outputs each correction value data DF to the ROM writer 45. When the delay time difference between the taps in the delay circuit 22 is denoted by τ, this correction value data DF is calculated by performing the calculation processing of the following expression (1).

Here, Hr1 (p, b) is a tap of the delay circuit 22 selected by the correction value data DF. In the case of a value of zero, it represents the center tap. In addition, Hr0 (p, b) displays the tab of the delay circuit 22 selected by the correction value data DF which is an initial value. In this embodiment, Hr0 (p, b) is set to zero. A is a constant. In this embodiment, a is set to a value of 1 or less (e.g., 0.7, etc.). Multiplication is performed so that the correction value can be surely converged even under the influence of noise or the like.

When the computer 44 stores the correction value data DF in the ROM writer 45 in this manner, the process proceeds to step SP12 to end this processing procedure. The computer 44 then executes a similar processing sequence for the falling edge of the digital binary signal, thus completing the correction table 20.

In the above configuration, the correction value tables 20 in the rising edge correction circuit 17A and the falling edge correction circuit 17B included in the optical disk device 1 (Fig. 1) are set to initial values. Under the same conditions as those for creating a conventional disk, an evaluation disk master 2 is generated (Fig. 4). From this disc master 2, a compact disc 41 for evaluation is produced.

In the evaluation compact disk 41, the laser beam L is turned on and off by an EFM signal whose signal level changes at a period corresponding to an integral multiple of the basic period T. The disk disc 2 is sequentially exposed to light, so that pits are formed. Thus, in the evaluation compact disc 41, the reproduction signal is subjected to intersymbol interference from adjacent pits and lands. Therefore, the timing at which the reproduction signal obtained from the compact disc 41 crosses the slice level changes depending on the shape of the pits and lands located before and after, that is, according to the change pattern of the EFM signal. Therefore, jitter occurs.

This compact disc 41 is reproduced by the compact disc player 42. The reproduction signal RF is converted into a digital signal by the digital oscilloscope 43. Thereafter, a binary signal, a decoded EFM signal, and a reproduction clock are generated by the computer 44. Further, for each edge of the binary signal from the compact disc 41, pits and lands located before and after the decoded EFM signal are detected, and the pattern of change of the EFM signal is detected. For each variation pattern, the amount of jitter at each edge relative to the reproduction clock is measured in time form.

In addition, these time measurement results are averaged over the change pattern. The amount of jitter caused by inter-signal interference is detected for each change pattern. The compact disc 41 uses the amount of jitter detected in this way and executes the arithmetic processing of equation (1) including the jitter correction unit based on the delay time difference τ between the taps of the delay circuit 22 (FIG. 3). . On the basis of the center tap of the delay circuit 22, the tap position of the delay circuit 22 capable of erasing the detected amount of jitter is detected. Data specifying this tap position is stored in the read-only memory as the correction value data DF. As a result, the correction value table 20 is formed.

By forming the correction value table 20 in this way, the audio data D1 and subcode data input from the digital audio tape recorder 3 (FIG. 1) are subjected to data processing prescribed by the modulation circuit 13, and the basic period T is unitized. The EFM signal S2 changes in signal level. The signal level is converted into the TTL level by the level converting circuit 15 of this EFM signal S2. Thereafter, the clock CK is reproduced by the PLL circuit 16. In the rising edge correction circuit 17A and the falling edge correction circuit 17B (FIG. 3), the signal is sequentially latched in the 13-stage latch circuits 19A to 19M to detect the change pattern.

In addition, the EFM signal S2 is input to the monostable multivibrator 21 from the latch circuit located at the center of the latch circuits 19A to 19M. The monostable multivibrator 21 is triggered at the timing of the rising edge in the rising edge correction circuit 17A and at the timing of the falling edge in the falling edge correction circuit 17B. In the rising edge correction circuit 17A and the falling edge correction circuit 17B, rising pulse signals and falling pulse signals are respectively generated in which the signal level rises at the timings of the rising edge and the falling edge, respectively.

The rising pulse signal and the falling pulse signal are sequentially delayed in units of the delay time tau used to calculate the correction value data DF in the delay circuits of the rising edge correction circuit 17A and the falling edge correction circuit 17B, respectively. The tap outputs of this delay circuit 22 are output to the selector 23. For the change pattern of the EFM signal S2 detected by the latch circuits 19A to 19M, when the correction value table 20 is accessed using the latch outputs of the latch circuits 19A to 19M, the corresponding correction value data DF is detected. do. By this correction value data DF, the contacts of the selector 23 are switched.

In order to correct the jitter detected by the evaluation compact disk 41, the rising edge signal SS and the falling edge signal SR, which are respectively corrected at the timings of the rising edge and falling edge of the EFM signal S2, are the rising edge correction circuit 17A and the falling edge. It is output from the selectors 23 of the edge correction circuit 17B, respectively. The rising edge signal SS and the falling edge signal SR (FIG. 1) are combined by flip flop 25. The signal level of the output signal S5 of the flip flop 25 is corrected by the level inverse transform circuit 26. As a result, a modulated signal S1 that is corrected at the timing of each edge of the EFM signal S2 is generated to correct jitter detected on the evaluation compact disk 41, that is, to reduce inter-code interference. By this modulation signal S1, the disk master 2 is exposed.

As a result, pits in which edge positions are corrected to cancel intersymbol interference on the disc disc 2 are sequentially formed. From this disc master 2, a compact disc with remarkably reduced jitter is produced in comparison with a conventional compact disc.

In the above configuration, the modulation signal S1 is generated by correcting the timing of the EFM signal S2 according to the change pattern of the EFM signal S2, and the disk master 2 is exposed to the light using the modulation signal S1. As a result, jitter caused by inter-signal interference that changes in accordance with the change pattern can be significantly reduced as compared with a conventional compact disc.

Further, at this time, a compact disc for evaluation is generated and correction value data DF is generated. Therefore, even when the conditions for creating the compact disc change, the compact disc can always be generated by the appropriate correction value data DF by newly deriving the correction value data DF.

Second Embodiment

6 is a block diagram showing an optical disk device according to a second embodiment of the present invention. In this optical disk device 50, the light quantity of the laser beam L is raised at a predetermined timing to expose the disk master 2 to light. As a result, wide pits are formed locally, and the reflectance of the compact disc is locally changed. The characters, images, and the like are recorded on the information recording surface of the compact disk in the optical disk device 50 so that the characters, images, and the like can be visually observed and confirmed. In the components shown in FIG. 6, the same components as those of the optical disk apparatus 1 described above with respect to the first embodiment are denoted by corresponding reference numerals, and the redundant description will be described.

That is, in this optical disk device 50, the character signal generation circuit 51 outputs the light quantity switching signal SC1 to drive the optical modulator 52 inserted in the optical path of the laser beam L, and accordingly The amount of light is controlled by switching.

As shown in Fig. 7, in the character signal generation circuit 51, the N-ary counter 53 is composed of a ring counter, and counts the FG signal FG to output the count value CT1. In the rotation period of the spindle motor 4, the count value is switched to zero. At this time, the track signal C1 is output.

The M-ary counter 54 is composed of M-ary counts for counting the track signal C1, and outputs a count value CT2. The character signal generation circuit 51 outputs count values CT1 and CT2 indicating positions of the disc master 2 in the circumferential direction and the radial direction, respectively, using the N binary counter 53 and the M binary counter 54. do.

The character signal generation table 55 is composed of a read only memory circuit which holds pixel values of various character information. The character signal generation table 55 outputs data of each pixel value by using the count values CT1 and CT2 as addresses. The data of each pixel value is formed by the data of each bit representing a character and an image to be recorded on the disc master 2 in a bitmap format.

The level converting circuit 56 sequentially latches data of sequentially input pixel values and outputs a signal level suitable for driving the optical modulator 52 (Fig. 6). In this embodiment, the optical modulator 52 is thus driven to switch the light amount of the laser beam L from 100% light amount to 85% light amount. As a result, as shown in Fig. 8, letters, images and the like are recorded on the surface of the disc.

If the amount of light of the laser beam L is controlled to be switched from the amount of light of 100% to the amount of light of 85%, the reproduction signal also changes. Specifically, as shown in Fig. 11, the amplitudes W1 and W2 of the reproduction signal change as shown in Figs. 9 and 10, respectively, which show the eye pattern of the reproduction signals using the light amount of 100% and the light amount of 85%. If you observe it as a continuous waveform, the slice level SL1 for accurately converting the reproduction signal to the binary value in the case of 100% light quantity is a slice for accurately converting the reproduction signal to the binary value for 85% light quantity. It is different from level SL2. That is, the asymmetry tree in the part obtained by the amount of light of 100% changes largely in it in the part obtained by the amount of light of 85%.

Conventional compact disc players have an automatic slice level adjustment circuit for correcting the slice level in accordance with such an asymmetry change. However, if the light quantity of the laser beam L is drastically changed to emphasize the outline so that the characters, images, etc. to be recorded can be clearly observed with the naked eye, it becomes difficult for the automatic slice level adjustment circuit to follow such a drastic change eventually. Therefore, a very long burst error occurs at the boundary portion of a character, an image, or the like.

Thus, in this embodiment, modulation signals S1A and S1B corresponding to light amounts of 100% and 85%, respectively, are output from the two edge correction circuits 57A and 57B. The modulation signals S1A and S1B are selected in conjunction with the switching of the light amount of the laser beam L by the data selector 58.

Therefore, in the optical disk device 50, the amount of light of the laser beam L is switched, and the modulation timing S1A or S1B is selected in accordance with the pit width that is changed so that the exposure timing of the laser beam is changed. As a result, the edge position at each pit changes in response to the change in the pit width. In the compact disc produced by the disc master 2, pits to which the same data is assigned are formed so as to have different pit widths in order to correct a change in the feedback light caused by the difference in the pit widths.

At this time, due to the change in the pit width, the degree of intersymbol interference for each light amount also changes. Thus, in accordance with the change pattern of the EFM signal S2, the timings of the modulation signals S1A and S1B are changed by the edge position correction circuits 57A and 57B, respectively. As a result, jitter is reduced. Thus, the edge position correction circuits 57A and 57B hold correction value data DF generated by the amount of light of 100% and 85%, respectively, in the correction value table.

As shown in Fig. 12 showing the results observed in the experiment, the change of the asymmetry can be effectively avoided by switching the timing of the modulated signal. Therefore, by the slice level SL, the reproduction signal obtained from the amount of light of 100% and the reproduction signal obtained from the amount of light of 85% can be converted into exactly binary values.

In the configuration shown in Fig. 6, the modulation signals S1A and S1B are switched by the data selector 58 in conjunction with the switching of the amount of light of the laser beam to switch the timing of the modulation signals. As a result, the reproduction signal can be converted into an exact binary value using a single slice level. Thus, errors can be effectively avoided and data can be reproduced accurately.

<Other Embodiments>

In the above embodiments, the case where the correction value table generated by using the evaluation compact disk is directly used to generate the compact disk has been described. However, the present invention is not limited thereto, and a new compact disc for evaluation may be newly created by using the correction table generated by the evaluation compact disc, and the correction value table may be modified by using the newly created evaluation compact disc. have. If the correction table is modified repeatedly in this way, the jitter can be surely reduced.

In the above embodiments, the case of detecting the change pattern by sampling the EFM signal 13 times has been described. However, the present invention is not limited to this, but if necessary, the number of sampling points may be increased to cope with a longer pattern of recording information.

In the above embodiments, the case of measuring the amount of jitter by measuring the time of the binary signal based on the basic clock and generating correction data from the measurement result has been described. However, the present invention is not limited thereto. In practice, when sufficient accuracy can be secured, correction value data may be generated by detecting a signal level of a reproduction signal based on a basic clock instead of measuring the amount of jitter using this time measurement. In this case, an error voltage from the detected signal level of the reproduced signal to the slice level is calculated, and correction value data is calculated from the error voltage and the transient response characteristics of the reproduced signal.

In the above embodiments, the case of correcting the timing of the modulated signal according to the correction value data stored in the table form has been described. However, the present invention is not limited thereto. In practice, when sufficient accuracy can be ensured, the correction value data may be calculated by arithmetic processing instead of the correction value data detected in advance, and the timing of the modulated signal may be corrected using the calculated correction value data.

In the above embodiments, the case where the correction value data is calculated using the evaluation compact disc has been described. However, the present invention is not limited thereto. For example, when applied to an optical disk device of write-once type, a correction value may be calculated based on the test recording result in the so-called test recording area.

In the above embodiments, the case where the present invention is applied to a compact disc has been described. However, the present invention is not limited to this, but can be widely applied to optical disk devices for recording various data using pits. The present invention can be widely applied to optical disk devices which are intended for multi-value recording of various data due to the difference in the transient response characteristic of the reproduction signal.

As described above, according to the present invention, the timing of the modulation signal is corrected according to the change pattern of the modulation signal. As a result, jitter caused by inter-signal interference can be reduced. The recording margin can be improved by that, and the recorded data can be reliably reproduced.

In addition, the timing of the modulation signal is corrected in conjunction with the switching of the light amount of the laser beam. As a result, the asymmetry is corrected and data can be accurately reproduced by a single slice level. In addition, deterioration of jitter caused by switching the amount of light of the laser beam can be effectively avoided. From these facts, it is possible to record images, characters and the like, and to reliably reproduce the recorded data.

Although preferred embodiments of the present invention have been described with reference to the accompanying drawings, the present invention is not limited to the above embodiments, and a person skilled in the art without departing from the spirit or scope of the invention as defined in the appended claims. It will be appreciated that various variations or modifications may be made.

Claims (2)

In the optical disk manufacturing method which makes a disk-type board | substrate from the stamper created based on the developed disk original material by exposing according to a modulation signal, and forms a reflective film and a protective film in this disk-shaped board | substrate, and makes an optical disk. Setting a correction value table on the basis of the reproduction result of the evaluation disk created from the evaluation disk original; An exposure step of switching the signal level of the modulated signal by an integer multiple of a predetermined basic period in accordance with the data to be recorded, and controlling the laser beam on and off by the modulated signal to record the data on the disc disc. and, And in the exposing step, correcting the timing of the modulated signal according to the correction data stored in the correction value table. 3. The reproduction result according to claim 1, wherein the reproduction result is the binarization of the fundamental period for each of the change patterns with respect to the binarized signal obtained by binarizing a reproduction signal obtained by reproducing the disc-shaped recording medium at a predetermined slice level. A manufacturing method of an optical disc, characterized by comprising a detection result of detecting timing of an edge of a signal.

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